Macro rustc_query_impl::plumbing::handle_cycle_error

macro_rules! handle_cycle_error {
    ([][$tcx: expr, $error:expr]) => { ... };
    ([(fatal_cycle) $($rest:tt)*][$tcx:expr, $error:expr]) => { ... };
    ([(cycle_delay_bug) $($rest:tt)*][$tcx:expr, $error:expr]) => { ... };
    ([$other:tt $($modifiers:tt)*][$($args:tt)*]) => { ... };
}